Artificial teeth



Nov. 23, 1965 B. CONNAN 3,213,711

ARTIFICIAL TEETH Filed July 17, 1962 INVEN TOR. GEORGE fieuci Con NANUnited States Patent 3,218,711 ARTIFHCIAL TEETH George Bruce Connan,Preston, Victoria, Australia, as-

signor to Dentsply (Australia) Proprietary Limited, Victoria, Australia,a corporation of Australia Filed July 17, 1962, Ser. No. 210,595 5Claims. (Cl. 32-8) This invention relates to artificial teeth and theirmanufacture. It is directed particularly to the production of artificialteeth which simulate natural human teeth and are to be used inintra-oral restorative devices.

Natural teeth comprise essentially a dentine core which is surrounded bya layer of tooth enamel. Observation discloses that natural teeth varyconsiderably in structure due to variations in the degree of opacity ofthe tooth, diminishing toward the incisal and marginal edges, and toirregularities in formation. It is these variations and irregularitieswhich, to a certain extent, impart the natural appearanc to naturalteeth. Developments in the art of manufacture of artificial teeth havebeen, from the cosmetic point of view, directed for many years towardthe reproduction of artificial teeth or" the characteristics andirregularities in appearance 'of artificial teeth.

One of the most important advances in this direction Was the production'of two-part teeth, molded from synthetic resinous material such asmethyl methacrylate, in which there was provided a body of opaquematerial, which simulated the dentine of natural teeth, and a partlyopaque, partly translucent veneer on the front or labial surface of theteeth, which simulated the enamel. One process for the production ofsuch teeth is described in the specification of Australian Patent No.119,646. In that process the enamel part is formed and cured then thedentine part is formed and the two parts brought together and given afinal curing to unite the two parts. In another process the two partsare formed together and only one curing is carried out. Production ofteeth by these processes enabled manufacturers more readily to simulatethe gradation in opacity of natural teeth from relatively translucentincisal and marginal edges to a substantially opaque body.

Further developments have led to the reproduction of various effects tosimulate the irregularity of natural teeth. Teeth have been producedwith irregular labial and incisal surfaces and vertically extendingstriations and other special effects have been induced to reproducecorresponding effects in natural teeth. Striations have been produced bya variety of means including, in the case where the tooth is formed bythe two-part method, the formation of an irregular interface between theenamel material and the dentine material. In other cases, columns orblades of relatively more opaque ma- .terial have been inserted in theteeth during manufacture.

These columns or blades extend upwardly from the incisal edge and havethe effect of producing relatively darker or more opaque verticallyextending areas simulating similar occurrences in natural teeth.

Other varying effects have been produced by introducing materials ofcontrasting shades into the tooth structure, at the boundary between thedentine material and the enamel material to produce areas of light anddark, so as to'attempt to produce de-calcified simulation effects. Ithas also been attempted to reproduce the pearly appearance of goodnatural teeth by the use of pearlescent "ice pigments dispersedgenerally throughout the enamel and dentine materials, but theseattempts have met with only very limited success, especially in regardto producing life-like effects.

While all of these advances have resulted in the production ofartificial teeth which extend more and more toward the apearance ofnatural teeth, one almost indefinable property of natural teeth has sofar eluded the copyist. So far, no artificial tooth has been producedwhich will simulat the live appearance of a good natural tooth. Thisinvention has as its principal object to capture that appearance of lifeand present it in an artificial tooth.

Our close study of carefully sectioned and preserved natural teeth hasdisclosed the existence of definite light reflection from the manyminute tubules which radiate out from the core of the tooth through thedentine and enamel toward the outer surfaces of the tooth. We haveobserved that those tubules which are angled to the direction ofincident light, when viewed from a suitabel position, present partlyreflective high spots which, in good natural teeth, appear through theenamel layer as gently shimmering pearlescent areas disposedparticularly adjacent the incisal edge of the labial surfac of theteeth. It is this phenomenon which, we believe, gives a good naturaltooth its live appearance. Thus far, however, it has not been possibleto reproduce in artificial teeth the means of natural teeth whichproduce such pearlescence.

The basic object of this invention, therefore, is to provide thesepearlescent-appearing areas in artificial teeth by arranging in anartificial tooth a partly reflective layer or seprated reflective areas,which are preferably of an uneven nature. Best results have so far beenobtained by including a partly reflective, partly translucent band-likelayer in a restricted or localized area or areas located preferably inthe incisal third of the tooth and adjacent the labial or buccalsurfaces. The layer has been successfully produced by the use ofpearlescent or pearl-like pigment applied, in the case of a two-parttooth, at the interface between the enamel material and the mor highlypigmented dentine material.

Details of the foregoing objects and of the invention, as Well as otherobjects thereof, are set forth in the following specification andillustrated in the accompanying drawing forming a part thereof.

In the drawing:

FIG. 1 is a front elevation of an exemplary artificial tooth embodyingthe principles of the present invention.

FIG. 2 is a vertical sectional view of said exemplary tooth as seen onthe line 22 of FIG. 1.

FIG. 3 is a transverse sectional view of said exemplary tooth as seen onthe line 33 of FIG. 1.

FIG. 4 is a view similar to FIG. 1,, but representing an exemplaryappearance of an artificial tooth embodying the invention as viewed fromthe front or labial surface thereof.

The invention may be readily practiced in the production of two-partdentine-enamel material teeth by utilizing processes such as thatdescribed in prior Australian Patent No. 119,646. Using that process,the enamel part 10 of the exemplary artificial anterior tooth 12preferably is first formed in the mold and then, while the enamel part10 is still in the mold, a small amount of pearlescent pigment, such asa thin band 14 thereof, is applied toselected areas of the preferablyuneven interface surface of the enamel which will mate with the dentineor body portion 16 of the tooth 12. This band is located preferably inthe socalled incisal third of the tooth which is spaced upward from theincisal edge or occlusal surface and more extensively spaced downwardfrom the gingival end 17 of the tooth. The pearlescent pigment forms amultitude of plane reflective surfaces to produce a mirror-like effect.As best seen in FIG. 3, the interface 18 of the enamel part 10 of thetooth is not a flat plane, or even a regularly curved surface in thepreferred construction. Rather, it is a series of connected irregularcurves, the axes of which are substantially parallel to the major axisof the tooth.

The advantage of such an irregular surface is that the reflection oflight through the irregular shape of the enamel part, or, rather, theenamel-simulating part, of the tooth produces a much more life-likeresult to the observer. In regard to the present invention, suchirregular surface 18 is especially advantageous in that the translucence of the enamel part permits light to be reflected from and alsopenetrate the band 14 or pearlescent pigment at different locations,depending upon the line of sight of the observer relative to the tooth.Typical lines of sight are represented by the arrows A, B, and C in FIG.3 and, from these, one readily can visualize the possible varigatedpattern effects which can be observed by a viewer. Thus, the desirableshimmering effect characteristic of normal pearlescence in an oystershell, mother of pearl, and similar substances, is apparent to theviewer and is of a type that occurs in most natural, healthy teeth atsubstantially the same location. Hence, the aforementioned lifecharacteristic is produced in artificial teeth by the present invention.

The pearlescent material may be pigments which are generally typified asoccurring or growing naturally in plate or plane form. One commercialexample is derived from fish scales and is available in two forms;platelets, which is the preferred form for use in accordance with thisinvention, and needles or fish paste, which gives a lesser opticaleffect. So-called pearl pigments may also be derived from oyster shelllining or other semi-translucent, semi-reflective materials which lendthemselves, naturally or otherwise, to partial reflection of incidentlight without excessive scattering and diffusion. Suitable artificialpearl pigment'material is available and has been used successfully intooth products made in accordance with the invention. These, generally,are lead salts of fatty acids and are flat, plate-like crystals in asuitable liquid or paste vehicle to render the pigment capable of readyapplication, preferably in the form of a band, to the desired tooth partby brushing, spraying, or the like. Spraying is highly effective toapply the pearlescent pigment material by masking those surface portionsof the tooth part upon which no pigment is desired, to produce band 14shown in FIG. 1, wherein it will be seen that preferably said bandextends from one side of the tooth to the other in a mesialdistaldirection.

The pigment may be suspended in a resin monomer of the material fromwhich the tooth is constructed, methyl methacrylate, for example, or ina polymer which has been pigmented with the material in powder form.Such suspension may be applied by a brushing technique, for example, bydepositing a drop from a looped wire. The pigment may also be applied indry powder form and, if desired, subsequently wetted with a fine monomerspray. Where the pigment is applied in suspension, the viscosity of thesuspension should be adjusted so that the plane surfaces of the pigmentparticles assume a preferred orientation in the plane of the layer.

After the pigment is applied to the interface of the premolded enamelpart 10, the dentine or body part 16 of the tooth is formed suitably bymolding and is integrally bonded to the enamel part 10, in accordancewith conventional practice. The pearlescent layer thereby isincorporated into the tooth at the deutine-enamel interface. Theirregular nature of such interface produces even more natural effectsthan if a relatively smooth surface were formed, such interfaceirregularity being preferably in both the incisal-gingival direction andthe mesial-distal direction, and produces a shimmering effect such asFIG. 4 depicts.

The pearlescent effect of this invention possibly can be achievedotherwise than by the use of the material described above as pearlescentpigments. Any pigment or material which will provide a multitude of tinyreflective areas to produce a partly reflective and partly translucenteffect may be used. Such effect, for example, is similar to thatproduced by a very thin silver plate or partial mirror-silvering. It is,of course, important above all to use a pigment material which will notbe detrimental to the tooth structure and which is light-stable. It hasbeen found, for example, that certain pigments of bismuth oxychlorideare not suitable since they turn black when exposed to ultravioletlight.

Experimental teeth produced by the process described above have beenfound to be most attractive and possess a marked appearance of life.

While the invention has been described and illustrated in its severalpreferred embodiments, it should be understood that the invention is notto be limited to the precise details herein illustrated and described,since the same may be carried out in other ways falling within the scopeof the invention as claimed.

I claim:

1. An artificial tooth formed from two parts comprising a relativelyopaque inner body part and an outer translucent enamel-simulating parthaving complementary interface surfaces and connected together, saidtooth having restricted area adjacent the incisal edge or occlusalsurface which is visible through said outer translucent part on thelabial surface of the tooth, said restricted area comprising asubstantially continuous band of pearlescent material interposed betweenthe interface surfaces of said connected parts and extendingtransversely across the body part of said tooth for substantially thefull width thereof and positioned closer to the incisal edge or occlusalsurface than it is to the gingival end of the tooth, the width of saidband being substantially less than half the length of said tooth, andsaid material being semi-translucent and semi-reflective and simulatingthe pearlescent effect of a natural tooth when light is reflectedthereby due to said material only partially reflecting incident lightwithout excessive scattering and diffusion thereof.

2. The artificial tooth according to claim 1 in which the complementaryinterface surfaces of said connected tooth parts are uneven and saidband of pearlescent material being relatively thin and shaped by saiduneven interface surfaces, whereby said band of material is similarlyuneven.

3. The artificial tooth according to claim 1 in which said inner andouter parts thereof comprise synthetic resin and said pearlescentmaterial initially being dispersed in a resin monomer compatible withthe resins of said tooth parts and suitable to facilitate the depositionof said pearlescent material on said interface surfaces prior to saidmaterial being bonded to said resin parts of said tooth.

4. The artificial tooth according to claim 1 in which said layer ofpearlescent material comprises small platelike particles of pearlescentmaterial, said particles being substantially parallel to the interfacesurfaces of the parts of said tooth against which they are positioned.

5. An artificial tooth comprising two parts connected together andhaving a restricted area adjacent the incisal edge or occlusal surfaceand visible on the labial surface thereof, said restricted areacomprising a layer of pearlescent material interposed between saidconnected parts and selected from the class consisting of fish scales,the lining of oyster shells, and the lead salts of fatty acids, wherebysaid layer of material simulates 5 6 the pearlescent effect of a naturaltooth when light is FOREIGN PATENTS reflected from said 00111. 993091944 France.

References Cited by the Examiner RICHARD A. GAUDET, Primary Examiner.

UNITED STATES PATENTS 5 ROBERT E. MORGAN, Examiner. 2,230,164 1/1941Myerson 328 X 2,419,084 4/1947 Myerson et a1 328

1. AN ARTIFICAL TOOTH FORMED FROM TWO PARTS COMPRISING A RELATIVELYOPAQUE INNER BODY PART AND AN OUTER TRANSLUCENT ENAMEL-SIMULATING PARTHAVING COMPLEMENTARY INTERFACE SURFACES AND CONNECTING TOGETHER, SAIDTOOTH HAVING RESTRICTED AREA ADJACENT THE INCISAL EDGE OR OCCLUSALSURFACE WHICH IS VISIBLE THROUGH SAID OUTER TRANSLUCENT PART ON THELABIAL SURFACE OF THE TOOTH, SAID RESTRICTED AREA COMPRISING ASUBSTANTIALLY CONTINUOUS BAND OF PEARLESCENT MATERIAL INTERPOSED BETWEENTHE INTERFACE SURFACES OF SAID CONNECTED PARTS AND EXTENDINGTRANSVERSELY ACROSS THE BODY PART OF SAID TOOTH FOR SUBSTANTIALLY